Local heating which heats a specific portion has been performed extensively in various technical fields. For example, in the field of medical treatment, treatments of blood circulation disorders, inflammation disease, neuralgia and the like are performed by applying high-frequency energy to an affected portion of a human body. Also, recently, it is known that cancer cells perish by heating cancer tissue to 43.degree. C. or more, and therefore medical treatment of cancer which locally heats the cancer tissue portion has been performed.
FIG. 20 shows a basic configuration of a conventional local heating apparatus which heats a human body for the purpose of treatment of cancer.
A pair of plane electrodes 91 and 92 are installed in a manner of sandwiching an affected portion 81. When high-frequency energy is applied to a pair of the plane electrodes 91 and 92 from a high-frequency power supply unit 93, the affected portion 81 is heated between the plane electrodes 91 and 92.
In this case, a fat layer exists on the surface of the human body, and this fat layer is particularly easy to be heated since it is positioned beneath the electrodes, and therefore cooling parts 94 and 95 are installed beneath the plane electrodes 91 and 92, and cooling water is circulated by a cooling apparatus 96. Thereby, the human body is prevented from suffering any adverse effect by unnecessary heating of the fat layer.
Conventional local heating apparatus using a pair of plane electrodes tends to heat the tissue having a high electric resistance, like the fat layer on the surface of the human body, more intensely than the tissue having a low electric resistance, and a deeper part of the human body apart from the electrode is harder to heat because the electric field (or displacement current) diffuses as it enters the human body. For this reason, there exist problems such that heating concentrated on a local portion is difficult to perform. Furthermore, local scalding of the normal tissue in the surface fat portion may result from long periods of heating.
For example, when the cancer tissue is heated at 43.degree. C. or higher, cells of cancer perish, but when the cells of cancer existing in the deep part of the human body are intended to be heated to 43.degree. C. or higher, in the conventional local heating apparatus, there is a risk that the tissue close to the plane electrode is heated to 45.degree. C. or higher which is the limit temperature thereof, and therefore, the cells of cancer located in the deep part cannot be heated satisfactorily. Thus, in conventional local heating apparatus, it is the present state that only the cancer existing near the surface of the human body can be treated.
Accordingly, the present invention provides a local heating apparatus which eliminates the deficiency of conventional local heating apparatus. The present invention provides apparatus for heating deep-seated parts of a body and for intensively heating a desired local portion, and a cavity resonator for local heating suitable for use in the apparatus.